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I. RENNERFELT.

ELECTRIC FURNACE.

non flL PatentedSept. 12, `192.

Ins/enfer: WM 7p Patented Sept.

IVAR RENNERFEIT, F 1)JIJ'RSHOLM, SWEDEN. 1

(GRANTED UNDER 'rmi rnvi To all rwhom, t may concern:

Be -it known that I, IvAR citizen of the Kingdom dent of Djursholm,

` ,minerale spannen Appiicano: iiiiyigiiglist 12, .11121; `fseiiiiiNo.4A 491,815.

RENNERrEL'r, a of Sweden,- andjresiin the county of Stoclc holms Lan andKingdom of Sweden'harle invented certain new ments in Electric Furnaceshave tiled ap lications in Swe glo. 49911 Germany 'July 27th,

1918, Patent 1919, Patent No.` tember 23rd, 1919, May 12th, 1920), aspecification.

and useful' Improvefor which VI en 'July 8th,

328233 1Switzerland -Sfepf- `Patent No.' iof lMy invention relates toimpi'bvements'in the construction crucible furnace Iand jh'as provide a"furnace especially suitablewfor melting such metalsl andalloysofmetals, which are to acertain extent easilygasied at rather lowtemperatures.

known in the art that electric 'melting -of yellow brass, centage ofzinc, nace of which if ,undertaken'in an arc furthe steel melting type,means'a'very contains va 'large` perundesirable evaporation of zinc,causing considerable losses.

One of the reasons for this is, that' the surface of the charge isexosedto intense heating 1n too close proximity therefore,

rate of heating,

inv as uniform all ab e and an excessive, ver ing is practically unavoiable'. cu ty is, furthermore, that the zinc gases from powerful 'arcs'to'the'metal.. The' 'is far from beover the charge as'desirharmfulrheat- The diiiienlargedby they fact after having beendeveloped are superheated by contact with the arcs and the electrodes,

tion inside of making a 'condensae furnace practically impossible. Inorder to avoid or at least reduce the amount of evaporation of zincfrom, to lapply charge 1n the heat obtain this object a shaft furnacefor instance, yellow brass I propose to the lower parts of the a mannersimilar to the well known in a kettle. To in a practical way I buildwith a lower heating chamber, provided with electrodes or other meansfor transforminfr electric energy into heat and an upper meltingchamber, which may consist of a shape. If desired crucible of anypreferred the melting chamber may be obtained by means of a partitioninserted in a suitable place in the shaft,

tion consisting o said partif a material, which 1s a sions oF 'rangerGanancia 1921, 41 sur. L., 1313.)

the partition.

'-Tfimpr've thetransmissio'n of heat the surface of theV artition shouldbe made as large jas possib e] forl practical reasons.

a crucible'isl used, the shape of same should be: rather wide andshallow, i. e., it should vmore resemble'a plate or a wash bowl than a'crucible 'such' as generally used in coke fired crucibleffurnaces. 'l

-f'Io'facilitate the use of Vvery wide crucibles'thebottomof'saine maybe supported by meansofone or more columns of referablycarbonelectrodes, standing on tiie bottom of they heating chamber orarranged in a crosswiseposition between op osite sides of fthe: furnace",shat. In tiie heating chamber one or moreelectrodes and bottomcontacts admit'ielectric energy in any preferreduway.A To improve theregulation of the, ower yat starting and under running conditions, thebottom of the heating chamber may 'becovered with a layer of carbon orgraphite in the form of a fine powder, which serves as a contactmaterial for the arcs from the electrodes and also as a steadyingresistance. To permit supervision of the arcs and refilling, whenneeded, of the contact powder, an openin should be pro vided in thewalls of the ieating chamber. The furnace may be built either for usewith a stationary crucible which is emptied by tilting the furnace or orusing a removable crucible, the furnace being nontilting. The formeralternative is generally to be preferred as the loss of heat isdecreased and the life of the crucible increased by not removing thecrucible from the furnace.

From a purely metallurgical point of view the melting condition in afurnace as described are very favorable. The heat readily penetrates thebottom of the melting room and by causing the charge to melt improvesthe Contact between the heat conducting partition and the upperunmelt'e'd parts of the charge. Ovcrheating of the charge 1s practicallyeliminated and, consequently, also gasifying of zinc, if the chargeoonsists ol' yellow brass. Should, however, metallic gases develop atthe bottom, no harm is done as the rate of evaporation will be fairlyslow. Furthermore, gases, which may develop, will, when risingupwardsthrough the charge, practically all condense when coming incontact with the upper comparatively cool parts of the char e. Themelting chamber may be perfectly c osed, as no electrodes enter same.This means that a considerable vapor pressure may be obtained, which,Vas wel] known in the art, prevents or lessens gasifying of the charge.

- A furnace built according to the present invention is illustrated onthe accompanying drawing in which Fig. 1 is a vertical Section, taken atlines X-X in Fig. 2, which is a vertical section taken at lines y inFig. 1. Similar letters refer to similiar parts in the several views.

A shaft furnace 1 is divided into two chambers, an upper crucible 2 anda lower heating chamber 3. The bottom 4 of the crucible is heated bymeans of arcs 5 generated by electrodes 6,v rejecting into the heatingchamber. On t e bottom of this a quantity 7 of graphite or carbon servesas a contact and resistance material. A bottom contact 8 may be employedfor the admission of the energy when desirable. An opening 9 in the sidewall of the heating chamber permits watchingv the arcs and ins troducingmore powder when required. On top of-the melting room a cover 10 may beemployed for heat insulating or other purposes. When using a very wideCrucible which is supported at the circumference a centrally locatedsupport 11 consisting of carbon or other suitable material may be pro`vided.

The heating of the Crucible in the man` ner stated is facilitated by thearcs being deviated upwards in the same way as described in LettersPatent No. 1103379 of the United States. The cause of the phenomenonapparently is an electrodynamic repulsion of small particles of carbonemanating from the electrodes and from the contact material at thepoints heated by the arcs.

Having now fully described my invention, I claim:

1. In an electric furnace having an upper chamber7 a lower chamber, withpoorly heat conducting walls, a heat conducting part1- tion between saidchambers and means for heating the lower chamber electrically thecombination with each other of at least two electrodes projecting into;the lower chamber, for the purpose of generating an electric arc in thelower chamber.

2. In an electric shaft furnace the combination of a lower heatingchamber having poorly heat conducting walls electrodes in said chamberfor heating same electrically a contact 4powder on the bottom of thechamber, a contact extending through said bottom and an upper meltingchamber consisting for instance of a graphite crucible.

3. In an electric shaft furnace the combination of a lower heatingchamber having poorly heat conducting, walls electrodes in said chamberfor heating same electrically and an upper meltin chamber consisting ofa crucible supporte on a refractory pro- {jection from the bottom of theheating cham- 4. In an electric shaft furnace the combination of a lowerheating chamber, an upper melting chamber and means for heating thelatter by cansinor electric arcs in the lower chamber to be eviatedupwards from the points of a lurality of electrodes projecting into thesaid) heatinr chamber.

Signed at Stockholm in the county of Stoekhollns Lan and State of Swedenthis 26th day of July A. D. 1921.

IVAR RENNERFELT.

Witnesses:

W. C. ERlKsoN, S. IvnnsoN.

